The present invention relates to a coating composition for the surface treatment of a rubber article or, more particularly, to a coating composition for the surface treatment of a rubber article which can be imparted with improved abrasion resistance and smoothness or lubricity on the surface by the treatment therewith. The invention relates also to a method for the improvement of the abrasion resistance and lubricity of the surface of a rubber article.
Needless to say, the application fields of rubber articles are so wide in the modern industries that some of the industries can no longer exist without rubber articles indispensable in various parts. Automobiles are built with a variety of rubber parts, of which weather strips of a cured rubber are used for waterproof sealing in the doors, windshields, rear windows, trunk room lids and elsewhere. Rubber-made weather strips in automobiles are used sometimes with rubbing on the surface or in contact with other parts in a sliding movement so that weather strips are required to have good abrasion resistance of the surface and good lubricity on the surface in order to decrease the friction thereon. One of the methods to meet this requirement is to coat the surface of the rubber article with a urethane resin-based coating composition disclosed in, for example, Japanese Patent Kokai No. 3-20376, No. 3-21675, No. 3-21676, No. 3-86774, No. 3-252477, No. 4-8778, No. 4-8779, No. 4-5580, No. 4-25581, No. 4-31474 and elsewhere or a silicone resin-based coating composition disclosed in Japanese Patent Kokai No. 4-90369, Japanese Patent Publications No. 56-47864 and No. 4-0072 and elsewhere.
The above mentioned urethane resin-based coating compositions are, however, not practically satisfactory for the purpose due to the relatively poor weatherability of the coating film formed therefrom so that the improvement in the surface properties of the rubber articles coated therewith is not durable enough. Though somewhat superior in the weatherability as compared with urethane resin-based coating compositions, the silicone resin-based coating compositions are also not quite satisfactory in respects of the adhesion of the coating film to the rubber surface and the abrasion resistance of the coating film. In addition, the surface lubricity of the rubber articles such as weather strips coated with a silicone resin-based coating composition is not so high that, when the weather strips are used in automobiles, creaking noises are sometimes generated from running automobiles due to the frictional sliding movement on the surface of the weather strips to decrease the pleasantness and safety of the drivers and passengers therein. Moreover, another important problem must be taken into consideration relative to the environmental pollution and workers' health and safety in automobile factories because the above described coating compositions are all in the form of a solution prepared using a large volume of organic solvents as a diluent which is dissipated into the atmospheric air in the step of drying of the coated surface to cause pollution of the working environment.